public class diedai {
    public static void main(String[] args) {
        int c = 0;        
        int tmp[] = new int[args.length];
        for (int i = 0; i < args.length; i++) {
            tmp[i] = Integer.parseInt(args[i]);
        }
        if (tmp[0] < tmp[1]) {
            System.out.println("wrong!");
            System.exit(0);
        }
        c=C(tmp[0],tmp[1]);
        System.out.println(c);
    }
    public static int C(int n,int m){
        if(m==0||m==n)
            return 1;
        else
            return C(n-1,m-1) + C(n-1,m);

    }
}
